Puas Rov Ua Dua Rau -Off Cycling of 316 Stainless Steel Sheath Immersion Heaters in Neutral Deionized Water Generate Weld Heat-Tshwj xeeb Zone Sensitization thiab Pitting Hauv qab 200 degree?
Tso lus
316 stainless hlau hluav taws xob cua sov raj yog qhov chaw ua haujlwm tsis zoo tshaj plaws nyob rau hauv qis -cov dej ua haujlwm deionised, txawm tias muaj cov tshuaj chloride qis dua 10 ppm. Cov ntaub ntawv qhia txog kev siv tshuaj dej-rau- txhaj tshuaj (WFI) rov ua dua lub voj voog qhia tau tias flange welds thiab raj-rau-kawg cap welds feem ntau raug cuam tshuam los ntawm intergranular nres thiab pitting tom qab 18-36 lub hlis ntawm kev ua haujlwm, txawm tias muaj ntau dua cm. Qhov kev coj cwj pwm no yog qhov tsis sib xws rau qhov kev xav tias tsis tshua muaj chloride, nruab nrab -pH dej tsis zoo rau austenitic stainless hlau. Qhov laj thawj tseem ceeb yog kev sib xyaw ua ke ntawm cov cua sov sib txuas- thaj chaw cuam tshuam (HAZ) rhiab heev thiab rov ua dua thermal cycling los ntawm kev siv lub tshuab cua sov sib txuas. Lub plhaub saum npoo kub sib txawv ntawm ambient thiab nominal setpoints ntawm 150 - 200℃rau WFI systems nrog txhua qhov ntawm - tawm lub voj voog. Lub voj voog no ua rau hauv thaj chaw chromium depletion ntawm cov ciam teb hauv HAZ, yog li ua rau cov cheeb tsam no raug cuam tshuam los ntawm cov kab oxidising molecules uas muaj nyob hauv cov dej ntshiab. Tsab ntawv xov xwm no suav txog qhov kev sib raug zoo ntawm cov keeb kwm ntawm cov khoom siv thermal, qib ntawm kev hnov qab, thiab pib pitting nyob rau hauv qis kub caij tsheb kauj vab los muab cov txheej txheem tshwj xeeb rau cov kws ua haujlwm qhia txog welded 316 stainless hlau immersion rhaub rau cov dej purity siab.
Rephrase kab lus
Rov qab mus rau qhov qub kab lus
Luam kab lus
Synonyms
keeb kwm,
yav dhau los,
cov hnub nyoog,
lub sijhawm dhau los,
xyoo,
sijhawm,
cov xwm txheej yav dhau los,
cov xwm txheej keeb kwm,
yav dhau los,
lub sijhawm dhau los,
keeb kwm tag nrho
kev kawm keeb kwm,
keeb kwm,
xyoo dhau los,
peb yav dhau los,
hnub nyoog,
cov centuries,
lawv yav tag los,
cuab yeej cuab tam,
keeb kwm yav dhau,
keeb kwm ntsiab lus,
cov xwm txheej dhau los
lub sijhawm,
lub sij hawm dhau los,
keeb kwm, thiab
cov xwm txheej keeb kwm
yav dhau los keeb kwm,
nws keeb kwm,
kawm keeb kwm,
keeb kwm thiab,
kev lig kev cai,
Metallurgical Mechanism ntawm Tsawg Kub Sensitization ntawm Welded 316 Stainless Hlau Sheaths
Lub rhiab heev ntawm 316 stainless hlau yog nkag siab tias yuav tshwm sim thaum raug kub ntawm 450℃thiab 850℃rau ntev txaus ua rau nag lossis daus ntawm chromium carbides ntawm grain ciam teb. Txawm li cas los xij, welding nyias phab ntsa sheath tube (nruab nrab phab ntsa tuab 1.0-1.6mm) ua rau HAZ me me uas txias sai heev los ntawm thaj tsam molten. Qhov HAZ no muaj qhov zoo ntawm cov chromium carbides tsim thaum lub sij hawm thermal voj voog ntawm vuam, tawm hauv ib cheeb tsam me me depleted ntawm chromium nyob ib sab ntawm txhua tus ciam teb. Nyob rau hauv ib puag ncig corrosive chloride ib puag ncig, qhov teeb pom kev zoo no yuav tsis ua rau tsis ua haujlwm tam sim. Txawm li cas los xij, ib qho kev sib txawv ntawm kev txhim kho hauv cov dej purity deionised uas muaj cov pa oxygen (feem ntau yog 5-8 ppm ntawm qhov kub thiab txias, txo mus rau 2-3 ppm ntawm 80 degree).
Rov ua dua thermal cycling ntawm chav tsev kub thiab 150-200 deg C speeds ob yam. Sib txawv thermal expansion pressures ntawm cov hlau weld (nrog me ntsis coefficient ntau dua vim cov qauv cam khwb cia) thiab lub hauv paus hlau tsim microcracking ntawm nyias chromium depleted grain ciam teb ua ntej. Thib ob, cua sov thiab cua txias twj tso kua mis me me ntawm cov dej deionised hauv thiab tawm ntawm qhov chaw tawg HAZ txhaum. Thaum cua sov, dej evaporates los ntawm cov microcrevices, tsom rau cov kab mob paug (xws li cov tshuaj chloride seem los ntawm kev tsim khoom lossis kev kho dej) los ntawm cov khoom ntawm 100-1000. Electrochemical muaj peev xwm ntsuas ntawm lub voj voog 316 stainless hlau weld qhia tias HAZ dhau los ua anodic rau cov hlau vuam thiab lub hauv paus hlau los ntawm 150-200 mV thaum lub sij hawm cua sov theem ntawm lub voj voog, tsim kom muaj lub zog corrosion ntawm tes.
Quantification ntawm Pitting Initiation Sijhawm hauv Weld HAZ Tests
Autogenous TIG welds (tsis muaj cov hlau muab tub lim) tau sim hauv de- dej ionized (resistivity 18 MΩ cm, yaj oxygen 6 ppm, pH 6.8, tsis muaj chlorides ntxiv) siv 316 stainless hlau raj kuaj nyob rau hauv kev kuaj mob ceev. Cov qauv raug thermally cycled los ntawm 25℃mus rau 180℃ntawm qhov cua sov ntawm 5℃/ min, uas yog ib qho ntawm cov cua kub lub voj voog. Txhua lub voj voog ua tiav yog tuav ntawm 180℃rau 30 feeb tom qab los ntawm cua txias rau 25 degree. Kev ua tsis tiav tau txhais tias pom tseeb pitting nyob rau hauv 50x magnification, los yog perforation raws li txiav txim los ntawm dye penetrant tshuaj xyuas.
Tsis muaj kev caij tsheb kauj vab, 180℃nruam immersion: Tsis muaj pitting tom qab 5000 teev. Tsis muaj thermal stress cycling ua rau HAZ tseem tsis muaj zog.
50 lub voj voog kub (~ 100 teev rhuab ua haujlwm). Tsis pom pitting. Electrochemical potentiodynamic reactivation (EPR) kev ntsuam xyuas pom tau tias qhov kev xav tau (DOS) ntawm 3% uas yog nyob rau hauv qhov kev txwv ib txwm muaj rau kev ua haujlwm corrosion.
200 lub voj voog thermal (kwv yees . 400 teev): Cov cim pib ntawm micro-pitting ntawm vuam HAZ. Pits < 20 µm hauv txoj kab uas hla tsuas yog pom los ntawm SEM. DOS nce mus txog 8 feem pua.
600 thermal cycles (kwv yees . 1200 teev) Pom pitting ntawm 10-15 qhov chaw raws HAZ ntawm ob sab ntawm cov hlaws weld. Qhov tob tob hauv qhov tob tshaj plaws: 0.3 hli ntawm phab ntsa qauv ntawm 1.2 hli (25% phab ntsa nkag). DOS: 14 feem pua.
70% piv txwv Ntau lub qhov perforations 1200 thermal cycles (~ 2400 teev) Qhov nruab nrab qhov tob: 0.9 hli, Los ntawm 1.2 hli phab ntsa. DOS > 20%
Hauv kev sib piv, tib cov qauv raug rau de- ionized dej nrog 50 ppm ntxiv sodium chloride (tseem hu ua cov tshuaj chloride tsawg) ua tsis tiav tom qab tsuas yog 250 lub voj voog uas qhia tias qhov kev xav tau kev sib koom ua ke nrog cov kab mob chlorides. Cov txiaj ntsig tseem ceeb yog tias txawm tias cov dej ntshiab deionised tsis pub muaj cov tshuaj chlorides uas tau ua rau pitting tsis ua hauj lwm tom qab 1200 cycles, tsuas yog vim muaj kev cuam tshuam rau hauv lub voj voog thermal -induced tawg hauv HAZ.
Cov nyhuv ntawm Weld Heat Input thiab Post Weld Treatment ntawm Cycle Life
Cov txheej txheem tsis zoo ntawm cov welding tseem ceeb txiav txim siab txog qib ntawm rhiab heev thiab tsis kam rau pitting hauv thermal cycling. Peb cov xwm txheej weld raug sim rau kev tsim khoom ntawm 316 stainless hlau sheaths:
Weld Condition Heat Input (kJ/cm) HAZ Dav (mm) Ntsuas DOS tom qab Vuam Thermal Cycles rau PerforationApplication pom zoo
High tshav kub input autogenous TIG (80-100 A, mus qeeb) 1.8 - 2.5 1.2 - 1.8 22% 180 - 300Tsis pom zoo rau tej lub luag hauj lwm caij tsheb kauj vab
Cov khoom siv hluav taws xob zoo li TIG (50 - 70 A, nruab nrab motion) 1.0 - 1.5 0.6 - 1.0 12% 600 - 900 Kev pab cuam qis dua 150 degrees C,<1000 cycles total
Pulsed TIG, low heat input (30-50 A, ceev ceev, muab tub lim yog xav tau) 0.5 - 0.8 0.3 - 0.5 5% 1800 - 2400 Pom zoo rau cov dej ntshiab huv, kev pabcuam cycled
Tsawg cua sov input + post weld tov anneal (1050 degree, dej quench) 0.5 - 0.8 0 (ua tiav recrystallised)<1% >10,000 (tsis muaj pitting pom los kuaj txiav) Qhov zoo tshaj plaws rau kev siv tshuaj WFI tseem ceeb
Cov kev daws teeb meem annealed tag tshem tawm rhiab heev tab sis feem ntau tsis tuaj yeem siv tau rau kev sib sau ua ke ntawm cov cua sov ua kom tiav vim tias cov hlau tsis muaj zog sab hauv (feem ntau NiCr 80/20) tsis tuaj yeem tiv taus 1050℃yam tsis muaj oxidation thiab seem deformation. Yog li ntawd, nyob rau hauv feem ntau ntawm cov fabricated heaters, qhov zoo tshaj plaws kev sib haum xeeb ntawm manufacturability thiab corrosion kuj yog tsawg tshav kub input pulsed TIG vuam nrog nruj tswj ntawm tshav kub input qis dua 0.8 kJ / cm.
Kev daws teeb meem engineering los txuas ntxiv Weld Life hauv De-ionized Water Cycling Service
Tsib txoj kev tsim thiab kev qhia tshwj xeeb tuaj yeem tiv thaiv lossis ncua sijhawm HAZ pitting tsis ua haujlwm thaum qhov chaw ua haujlwm muaj deionised lossis thim rov qab osmosis dej nrog kev sib tshuam ntawm lub tshuab cua sov. Txhua pawg ntawm cov welds yuav tsum tsim nyog los ntawm EPR xeem raws li ASTM G108 los ntawm cov chaw tsim khoom siv cua sov nrog qhov siab tshaj plaws tau tso cai DOS ntawm 8% rau cov kev pabcuam dav dav lossis 5% rau kev siv tshuaj. 2. Yuav tsum tau vuam nrog cov roj thaiv thaiv (argon lossis nitrogen) nyob rau sab hauv txoj kab uas hla ntawm cov hlua khi uas siv tau. Qhov no tiv thaiv oxidation ntawm sab hauv weld cag uas hauv zos depletes chromium. Thib peb, sau ntawv tshaj tawm -weld mechanical polishing ntawm sab nraud HAZ cheeb tsam mus rau qhov chaw tiav ntawm Ra <0.4 µm. Polishing tshem tawm cov txheej txheej nyias nyias qhov twg chromium depletion yog qhov hnyav tshaj plaws. Kev ntsuam xyuas hluav taws xob qhia tau hais tias polishing lub vuam nrog qhov pib DOS ntawm 12% txo qhov ua tau zoo DOS ntawm qhov chaw mus rau 6%, ob npaug ntawm lub neej thermal voj voog. Plaub, tsim kom muaj ib qho kev ua haujlwm niaj hnub los txo tus naj npawb ntawm thermal cycles. Qhov no yuav tsum suav nrog kev ncig tsis tu ncua lossis qis- lub zog sawv ntsug- los ntawm hom es tsis ua tiav kaw - ntawm lub rhaub. Lub chaw kho mob tau hloov pauv los ntawm -tawm kev tswj hwm mus rau qhov sib npaug ntawm qhov ntsuas kub ntawm 60 degree, thiab qhov vuam tsis ua haujlwm tau txo qis ntawm 15% hauv ib xyoos mus rau qis dua 1%. Thib tsib, yuav tsum muaj kev daws teeb meem ntawm txhua qhov sib txuas welded tom qab vuam thiab ua ntej kev sib dhos zaum kawg rau kev teeb tsa tshiab yuav tsum muaj ntau dua 2000 qhov kub thiab txias nyob rau hauv kaum{25}} xyoo lub neej, txawm tias ob-theem fabrication txheej txheem nrog re- vuam ntawm cov khoom sab hauv yog yuav tsum tau.
Welding Quality Specification for Long Term Reliability of High Purity Water Heaters
Thaum qhia txog 316 stainless hlau hluav taws xob immersion rhaub rau dej deionised, thim rov qab osmosis permeate los yog distilled dej cov kev pab cuam, engineers yuav tsum tau hais kom meej weld zoo qauv ntawm qhov yuav specification. Thov muab cov ntawv luam ntawm cov ntaub ntawv tsim nyog cov txheej txheem weld (WPQR) uas suav nrog cov kev ntsuas cua sov thiab qhia cov txiaj ntsig ntawm EPR ntawm daim coupon welded nrog tib qhov chaw. Rau cov xwm txheej uas qhov kev siv lub tshuab ua kom sov lub voj voog ntau dua ob lub voj voog ib hnub, cov khoom siv hluav taws xob tsis tshua muaj zog TIG vuam nrog qhov siab tshaj plaws cua sov ntawm 1.0 kJ / cm3 thiab siab tshaj HAZ dav ntawm 0.7 hli yuav tsum tau. Nyob rau hauv cov cheeb tsam uas cov resistivity ntawm dej siab tshaj 1 MΩ.cm (conductivity tsawg dua 1 µS / cm), qhia tias tag nrho cov wetted welds yuav electropolished kom tshem tawm 20-30 µm ntawm cov khoom nto. Qhov no yuav tshem tawm cov txheej txheem chromium feem ntau. Los ntawm kev kho weld rhiab heev raws li ib tug loj tsis ua hauj lwm mechanism, es tsis xav hais tias tsawg chloride paub tseeb corrosion kuj, engineers muaj peev xwm tau txais kev pab cuam lub rhaub nyob rau hauv ntau tshaj kaum xyoo nyob rau hauv nyuaj high-purity dej voj voog daim ntawv thov.
